Tamoxifen
Tamoxifen (Nolvadex)
Tamoxifen
(tah- MOX-ih-fen)
Pregnancy Category: D Apo-Tamox Gen-Tamoxifen Nolvadex Nolvadex-D Novo-Tamoxifen Tamofen Tamone (Rx)

Classification: Antiestrogen

See Also: See also Antineoplastic Agents .

Action/Kinetics: Antiestrogen believed to compete with estrogen for estrogen-binding sites in target tissue (breast); also blocks uptake of estradiol. Steady-state plasma levels (after 10 mg b.i.d. for 3 months): 120 ng/mL for tamoxifen and 336 ng/mL for N-desmethyl tamoxifen. Steady-state levels, tamoxifen: About 4 weeks; for N-desmethyltamoxifen: About 8 weeks ( t 1/2 for metabolite: about 14 days). Metabolized to the equally active N-desmethyltamoxifen. Tamoxifen and metabolites are excreted mainly through the feces. Objective response may be delayed 4-10 weeks with bone metastases.

Uses: Adjuvant treatment of axillary node-negative or node-positive breast cancer in women following total or segmental mastectomy, axillary dissection, and breast irradiation. Metastatic breast cancer in premenopausal women as an alternative to oophorectomy or ovarian irradiation (especially in women with estrogen-positive tumors). Advanced metastatic breast cancer in men. To reduce the incidence of breast cancer in high-risk women, taking into account age, previous breast biopsies, age at first live birth, number of first-degree relatives with breast cancer, age at first menstrual period, and a history of lobular carcinoma in situ. Investigational: Mastalgia, gynecomastia (to treat pain and size), pancreatic carcinoma, advanced or recurrent endometrial and hepatocellular carcinoma.

Contraindications: Lactation. Concomitant coumarin anticoagulant therapy or women with a history of deep vein thrombosis or pulmonary embolus.

Special Concerns: Use with caution in clients with leukopenia or thrombocytopenia. Women should not become pregnant while taking tamoxifen. Although the risk of breast cancer is significantly lowered, this benefit must be weighed against an increased risk of endometrial cancer, pulmonary embolism, and DVT. Safety and efficacy have not been determined in children.

Side Effects: GI: N&V;, distaste for food, anorexia, diarrhea, abdominal cramps. CV: Peripheral edema, flushing, superficial phlebitis, DVT, pulmonary embolism, thromboembolic disorders (especially when tamoxifen is combined with other cytotoxic agents). CNS: Depression, dizziness, lightheadedness, headache, fatigue. Hepatic: Rarely, fatty liver, cholestasis, hepatitis, hepatic necrosis. GU: Hot flashes, vaginal bleeding and discharge, menstrual irregularities, amenorrhea, altered menses, oligomenorrhea, vaginal dryness, pruritus vulvae, ovarian cysts, hyperplasia of the uterus, polyps, uterine carcinoma. Other: Skin rash, skin changes, hypercalcemia, musculoskeletal pain, hyperlipidemias, weight gain or loss, increased bone and tumor pain, mild to moderate thrombocytopenia and leukopenia, retinopathy, hair thinning or partial loss, fluid retention, coughing. In men, may be loss of libido and impotence, after discontinuing therapy.

Laboratory Test Alterations: Serum calcium (transient), thyroid-binding globulin in postmenopausal women, BUN, AST, alkaline phosphatase, bilirubin, creatinine.

Drug Interactions: Anticoagulants / Hypoprothrombinemic effect Bromocriptine / Serum levels of tamoxifen and N-desmethyl tamoxifen Cytotoxic drugs / Risk of thromboembolic events

How Supplied: Tablet: 10 mg, 20 mg

Dosage
?Tablets Breast cancer.
10-20 mg b.i.d. (morning and evening) or 20 mg daily. Doses of 10 mg b.i.d.-t.i.d. for 2 years and 10 mg b.i.d. for 5 years have been used. There is no evidence that doses greater than 20 mg daily are more effective.
Reduction in incidence of breast cancer in high-risk women.
20 mg/day for 5 years.
Mastalgia.
10 mg/day for 4 months.